Hi Everyone, If you are willing to help me out i have some loose connectors on my 1990 f250 7.5L 4x4 zf5-42. PO said that they swapped in a 1992 7.5L but as far as i can tell kept the 1990 wiring harness. If you can help me identify these connectors I would greatly appreciate it! FWIW the truck has a 5th wheel hitch and was equipped with a trailer brake which was removed, i plan on reinstalling one eventually. note that they are labeled 1,2,3,4 if you would respond likewise. Thank you!!!!!!



#1) this is located right under neath the driver's side right underneath the steering column near the ECM/fuse box, etc.




#2) this one is also underneath the drivers side hanging off the main wiring bundle that runs up to the fuse box




#3) this one is right next to the junction of the zf-42 and the bw1356 and follows the harness that includes the backup light sensor, 4x4 indicator light, o2 sensor, etc. all those are plugged in however.




#4) this one is hanging out right near the wiring to the hood lamp and the brake booster/master cylinder.

 

#1 looks like the RABS diagnostic wire and #3 may be for the VSS. I'm not sure about the other two.

 

Thank you. sorry but what is a VSS?

 

Vehicle Speed Sensor on the diff

 

Here's the under hood diagram

 

#1 Looks like some sort of diagnostic or mode-enable connector.
#2 MIGHT be for a trailer brake controller, what are the wire colors?
#3 No idea unless you have electric-shift 4x4, then it might be for the manual 4x4 sense.
#4 Looks like it's for an oxygen sensor, judging by it's shape and pin arrangement.

How many points do I get/lose for each correct/incorrect guess?

 

I need to play this game with my truck.....that under hood diagram looks extremely helpful. Where could I find one for a 1987 7.5L?

 

Thanks Daddylee100, do you have the diagram for a 1990? they kept the 1990 harness. thank you

 

#1 is the RABS test connector How to: Retrieve ABS trouble codes - Ford F150 Forum - Community of Ford Truck Fans

#2-the PO had a trailer brake hand wired in the truck, i took all those wires out--unless this is some sort of factory harness?
#3-i have manual shift with manual hubs. There is already a 4x4 sensor connected.
#4- you are correct that it looks like the o2 sensor plug, there is a pigtail that connects the o2 and both of those connectors look exactly like #4, but that's not it.

 

Thanks yes #1 i found is the RABS Test Connector.

#3 is consistent with VSS however my trucks speedo cable has a gear that turns off of the transfer case. So not sure why it would have a VSS connector unless that was just a wiring harness they grabbed "off the shelf" at the assembly line

or if I <i>should</i> have a VSS, what would it's purpose be? would that be to trigger the RABS? If so my abs light does not stay on that would be consistent with a RABS DTC.

 

The VSS would be where the speedometer cable attaches to the transfer case. I believe it was used for cruise control and for input into the engine computer. If you don't have cruise, the VSS may not be used and #2 could potentially be a connector that would be used for the cruise control amplifier. RABS speed sensing used the sensor on the rear differential.

VSS: Ford Ranger Speedometers - How They Work

 

#1 is the RABS self test connector, wire should be black with orange tracer

#2 is for the factory cruise option

#3 is for the either the vss or 4x4 switch, the vss has to be there for the computer to work right and for cruise control.

#4 is either the hood light connector or for the vss to the computer, if you have a working hood light, it will be the vss. Should be pink and green wires I believe and may have tracer colors.

#5 not shown as you will find it on the drivers side fender area closer to the cab and will be a small round black 4 pin female plug and should have a cap on it, two wires red/black and green/black, this is for the RABS sensor test connector.

#6 not shown will be close by #5 and will be a large round black male 4 pin plug with 3 wires, red, yellow and black and is for the trail tow harness.

 

Cool Thanks for the input.

I do not have cruise control, and the hood light is already connected. I recently replaced the clutch and as a result removed the transmission and transfer case, i did not see any ports that would accept connector #3 on either the trans or transfer case. is it possible then if my truck is not equipped with cruise control (it is not) that it would not be connected? I know that the rear diff has a RABS sensor and to the best of my knowledge it is connected. If #2-6 are supposed to be hooked up then i can proceed to the RABS diagnostic test i suppose. Reading other forums about VSS my truck drives just fine and the speedo works, etc. I've never had to "slam" on brakes thankfully but maybe i should take it to an empty parking lot and try it.

 

The transfer case VSS was mainly used for cruise control, so if there isn't cruise, the wires would be just left disconnected. The RABS wheel speed sensor is completely separate from the VSS on 87-91 trucks.

 

#4 Looks like the connector I found on my '92 F150 4x4. I found that it connected to the top of the transmission underneath the truck. It was a sensor for my reverse lights. As soon as I spliced some wires and plugged it in, bingo! I now have reverse lights. What color are these wires?

Edit: IIRC, I believe the wires were darker in color with a pink stripe. I will double-check that if you need.